Recursive-Diff
A JavaScript library (with TypeScript support) to find diff between two JS Objects/Array, support for complex nested JS Objects
This library can be used to get diff between two JS Objects/Arrays(or other primitive values). Diff are returned in the form of Array where each ARRAY item represents a change in the original Object/Array. A diff item can have following three properties:
-
path: An array representation of nested path -
op: Can be any one of the following - add, update or delete -
val: New value after change
const rdiff = require('recursive-diff');
const initialVal = {
a: {
b: 1,
c: 2,
d: [1]
}
}
const changedVal = {
a: {
b: 2,
d: [1, 2],
},
};
const diff = rdiff.getDiff(initialVal, changedVal);
/***
Diff of initialVal and changedVal is: [
{
"path": [
"a",
"b"
],
"op": "update",
"val": 2
},
{
"path": [
"a",
"c"
],
"op": "delete"
},
{
"path": [
"a",
"d",
1
],
"op": "add",
"val": 2
}
]
**/
const c = rdiff.applyDiff(initialVal, diff);
assert.deepEqual(c, changedVal);Api details
-
getDiff(oldVal, newVal, keepOldVal?):getDifftakes following parameters-
oldVal (required): initial value, can be Array/Object or even primitive type such as number, boolean or string -
newVal (required): changed value ( required ), can be Array/Object or even primitive type such as number, boolean or string -
keepOldValueInDiff (optional): boolean parameter which if set to true, every diff value will have an additional propertyoldValuewhich will denote the old value before mutation
-
-
applyDiff (oldVal, diff, visitorCallbackFn?)applyDifftakes three arguments:-
oldVal (required): original value, -
diff (required): diff returned bygetDiffAPI -
visitorCallbackFn (optional): This callback function is called at each depth level while applying the diff. It can be used to mark the mutation path with some meta properties eg:{ isMutated: true }. For more details, please check the examples directory of this repo.
-
Using recursive diff library in Node
- Install library using the command :
npm install recursive-diff - sample code is given below
const diff = require('recursive-diff');
const oldVal = {a:1};
const newVal = {a:2};
const delta = diff.getDiff(oldVal, newVal);
const ob3 = diff.applyDiff(oldVal, delta);
assert.deepEqual(ob3, newVal);Using recursive diff library in the Browser
'dist/recursive-diff.min.js' can be directly injected into a HTML page using the URL https://unpkg.com/recursive-diff@latest/dist/recursive-diff.min.js. Once it is included into the HTML file, diff API is accessible using window.recursiveDiff. Example given below.
<script type="text" src="https://unpkg.com/recursive-diff@latest/dist/recursive-diff.min.js"/>
<script type="text/javascript">
const oldVal = { a: 1 };
const newVal = { a: 2 };
const delta = recursiveDiff.getDiff(oldVal, newVal);
const ob3 = recursiveDiff.applyDiff(oldVal, delta); //expect ob3 is deep equal to newVal
</script>Using recursive diff library in TypeScript
import { getDiff, applyDiff, rdiffResult } from 'recursive-diff';
const oldVal = [1, 2];
const newVal = [2, 3, 4];
const diff:rdiffResult[] = getDiff(oldVal, newVal);
console.log('diff', diff);
const final = applyDiff(oldVal, diff);
console.log('applydiff', final); // final should deep equal to newValTests
Unit test can be run using the command npm test. This repo has more than 99% code coverage.
Examples
You can find more examples in the example folder of this repo. Few of the examples are listed below.
/* eslint-disable no-param-reassign */
/* eslint-disable no-console */
import { getDiff, applyDiff } from '../dist/recursive-diff';
let [a, b, c, delta] = [];
// testing primitive data type
a = 3;
b = 10;
delta = getDiff(a, b);
console.log(delta);
// Output: [{path: [], op: 'update', val: 10}]
c = applyDiff(a, delta);
console.log(c); // Output: 10
// testing array
a = [1, 2];
b = [1, 30, 40];
delta = getDiff(a, b, true); // third parameter : keepOldValInDiff, see output below
console.log(delta);
/** *
Output:
[
{ path: [1], op: 'update', val: 30, oldVal: 2 },
{ path: [2], op: 'add', val: 40 },
]
* */
c = applyDiff(a, delta);
console.log(c); // Output: [1,30,40]
// testing objects
a = {
a: '10',
b: '20',
c: '30',
};
b = {
a: '10',
b: '40',
};
delta = getDiff(a, b);
console.log(delta);
/** * Output:
[
{ path: ['b'], op: 'update', val: 40 },
{ path: ['c'], op: 'delete', val: undefined },
]
* */
c = applyDiff(a, delta);
console.log(c); // Output: {a:'10', 'b':40}
// testing complex deep object
a = {
b: [1, 2, [3, 4]],
c: {
c1: 20,
c2: {
c21: 'hello',
},
c3: 'India',
},
};
b = {
b: [1, 2, [4]],
c: {
c1: 20,
c2: {
c21: 'hi',
c22: 'welcome',
},
c3: 'cosmic',
},
};
delta = getDiff(a, b);
console.log(delta);
/**
Output:
[
{ path: ['b', 2, 0], op: 'update', val: 4 },
{ path: ['b', 2, 1], op: 'delete', val: undefined },
{ path: ['c', 'c2', 'c21'], op: 'update', val: 'hi' },
{ path: ['c', 'c2', 'c22'], op: 'add', val: 'welcome' },
{ path: ['c', 'c3'], op: 'update', val: 'cosmic' },
]
* */
c = applyDiff(a, delta);
console.log(c);
/** *Output
{
b: [1,2,[4]],
c: {
c1 : 20,
c2 : {
c21: 'hi',
c22: 'welcome'
},
c3: 'cosmic'
}
}
* */